The applicant has already proposed in the past a solution for considerably increasing the efficiency of the cooling system, this solution consisting briefly in cooling not only the secondary circuit of the transformer but also its primary circuit, by dividing it into several separate parts or sections by means of one or more turns of the secondary circuit, themselves directly cooled by an appropriate cooling circuit and in thermal contact with said parts of the primary circuit; in other words, this older solution consisted in incorporating one or more cooled turns of the secondary winding of the transformer in the winding of the primary, to cool this latter also.
As for the cooling circuit, it was formed for example as a duct through which a cooling fluid flows, and it was incorporated, for example by being brazed, between two juxtaposed parts of the copper and possibly aluminium strip, wound about the core and forming the turn(s) of the secondary circuit, and this according to any appropriate technological procedure.
This solution has proved satisfactory in numerous cases, but progress in the technique, more especially in the field of high-speed automatic welding by robots, has shown the limits thereof and has made it necessary to improve it again so as to further increase the cooling efficiency, while maintaining, which is particularly indispensable in this precise case of use, the option of being able to use space-saving, high efficiency transformers whose weights are as reduced as much as possible, so as not to reduce the intrinsic performances of the robots.
Now, one cannot hope to exceed a certain degree of cooling by simply extrapolating the older solution which has just been described and by dividing the winding of the primary into a larger number of parts or sections, for that would automatically lead to increasing also the number of cooling turns of the secondary circuit required for separating these sections, which is impossible, this number being itself imposed by the transformation ratio, for a given number of turns of the primary.